Method and arrangement op directional wave reception and emission



March 13, 1928. 1,662,247

- w. HAHNEMANN ET AL METHOD AND ARRANGEMENT OF DIRECTIONAL WAVE RECEPTION AND EMISSION Filed Sept. 26. 1925 3 Sheets-Sheet March 13, 1928.

. w. HAHNEMANN ET AL METHOD AND ARRANGEMENT OF DIRECTIONAL WAVE RECEPTION AND EMISSION Filed Sept. 25v 1925 3 Sheets-Sheet 1 arch 13, 1928. v 1, 62,247

w. HAHNEMANN ET AL METHOD AND ARRANGEMENT OF DIRECTIONAL WAVE RECEPTION AND EMISSION Filed Sept. 25,1925 3 Sheets-Sheet 3 FIG //c INYE'NTOR u A 13 r "W W ATTORNEY Patented Mar. 13, 1928.

UNED STATES PATENT FFHCE.

WALTER HAHNEMANN, OF KITZEBERG, NEAR KIEL, AND HEINRICH HECHT AND BERNHARD NIELSEN, OF KIEL, GERMANY, ASSIGNORS TO SIGNAL GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, OF KIEL, GERMANY, A FIRM.

METHOD AND ARRANGEMENT OF DIRECTIONAL WAVE RECEPTION AND EMISSION.

Application filed September 26, 1925, Serial No. 58,943, and in Germany October 6, 1924.

The present invention deals particularly with the method of arrangement of receiv ers and senders for directive and binaural listening, and directive sending, respectively.

In the prior art, the use of a plurality of receivers and senders is well known for directive sending and also for binaural reception. However in none of the previous uses of a plurality of receivers has it been atteniptedto obtain the most effective spac ing for the purpose desired.

As will be seen in the following discussion, the advantages obtained in the proper spacing is applicable to many useful purposes. According to the present method it is possible to arrange upon the mast or tunnel of a vessel, vertically, a plurality of high powered diaphragm whistles or air oscillators in such a manner that the passengers walking about the deck or, in fact, anywhere upon the vessel will not be troubled by the sound when the whistles are in operation. But for reflections it is possible that their operation may not be heard.

Likewise for directive transmission under water it is possible to arrange a system for sound senders so that a receiver placed very near the senders will not be afiected by the operation of the sender. This method is especially useful in depth sounding, in that the receiver and sender may be placed close together, as is always desirable, and yet be in a position where the sounds of the senders do not reach the receiver.

A further usefulness of the present system is the prevention of ambiguity in binaural direction determination where the source which is bein detected is a sustained note or one which is not greatly damped, so that a balance will be obtained from two successive vibrations of the note as well as the same vibration.

A further purpose of the present invention is that a minimum binaural base length may be obtained by allowing some of the receivers to serve both for the left and right ear compensation.

While it is evident that there are many other useful purposes to which the present invention may be applied, only a few above have been stated, the rest being disclosed from further discussion and description in Figure 5 represents the intensity curve of the live receivers at proper distances.

Figure (3 shows the application of Figure 5 for directing the sound within a zone.

Figure 7 shows the combination of vertical and horizontal receivers.

Figures 8a, Z) and 0 show how various directive and uniform distributional effects may be obtained.

Figure 9 shows the application to screening receivers or senders.

Figure 10 is a side view of Figure 9.

Figures 11a, 1) and 0 show the application of the principle to binaural listening in which a shortencdbase is also obtained.

Figure 12 shows the application to compensation.

The applicants have discovered that if similar sound emitting devices operating at the same phase with respect to each other are spaced in a straight line at a distance equal to the wave length of the sound emitted multiplied by the expression where n is the number of emitters, then there will be no sound heard along the line of the emitters or senders. The applicants have further discovered that the greater the number of senders 01' receivers, since one is really the reverse operation of the other, in such a line the more directive the sending or reception becomes, especially in the direction perpendicular to the axis of the senders or receivers. The applicants have further discovered that in the case of the before mentioned condition being fulfilled, the greatest possible portion of the energy emitted from the group of senders or received by the group of receivers is chiefly concentrated in the plane perpendicular to the base line and that auxiliary maxima,-

( l sin 72B sin 9 (2) where 9 where a: is the linear phase difference between successive receivers due to the direction of the wave front and compensation between receivers (here receivers and senders are used interchangeably) and where a is the wave length of the sound. The expression (1) has a maximum when 6 0, another when 9 17 or any whole multiple of 1r. In order to prevent a double maximum from occurring, it is necessary therefore to make 9 1r. A minimum will occur when n9=K1r where K n, where K is any whole number. If K were equal to n or greater then 6 would not be less than 71'. Assume K=n1 which will give the greatest range of 9 without allowing two maxima then or that the linear phase difference between successive receivers due to direction of the wave front and. compensation should be In evaluating a; it IHUSt be remembered that .it has two component efiects and may be written (6) x=d'(sin qbw+sin qS.) where d=the spacing between receivers.

bw=the angle of the .wave front with the line of receivers =the additional angle of retardation due to compensation. Where there is no compensation connected in the receivers or senders =O and maximum value that that a: can obtain under these circumstances is d.

When there is compensation added, the

maximum value of w=2d so that under these circumstances the spacing of the receivers 1s just half as great or (without compensation) A (with compensation) Figure 1 shows a section in the plane including the line of two receivers or senders at a distance of i. e. in this case of trom one another. The directional eflect is in this case rather faint. No auxiliary maxima exist. The polar vector OA shows the intensity perpendicular to the line of receivers. This case is well known and dedescribed only for elucidation purposes.

The directional effect is too small for practical use.

Figure 2 shows a section in the plane including the line of three receivers or senders each at a distance of The polar vector OA represents the intensity in the direction perpendicular to the line of. receivers, the vectors OB and O0 in their respective directions. If the spacing had been a Wave length the efiect would not be very directive, there existing under these conditions four maxima of about equal intensity covering a broad angle as shown in Figure 3.

Figure 4 shows the intensity curve of five recelvers spaced distance apart. curve that the intensity of the large maximum is greater'than those of next in order. In fact, since in Figure 4: the vectors are simply the current vectors, the intensities vary as their squares, in which case it is apparent that all but the maximum loop are negligible.

' Figure 5 shows the intensity curve for the case n=3 and from the differ It will be seen from the I distribution perpendicular to the line of receivers is obtained only in the case In Figure 6 is shown the application of such a definitely spaced set of units to directional sending. The senders 1, 2, 3, 4 and 5, which may be of the oscillator type, may be arranged vertically upon the mast of a vessel and operated simultaneously. In this manner the maximum sound 100 will be within the angular opening shown in the figure, which in the case of five senders is about 29, and the intense sound vibration which otherwise is felt all over the vessel will be confined to a zone outside of that used by the passengers.

Figure 7 illustrates the grouping for obtaining a combination of directive effects. By using the proper combination of receivers directive effects can be obtained as shown in Figure 8, 8 and 8.

Figures 9 and 10 show the application by which directive effect and screening may be obtained in cases where one set of apparatus are desired to be shielded or unaffected by the operation of another. In this case the receivers or senders a and b respectively may be arranged horizontally along the vessel in such amanner that the maximum loop is directive in the angle shown. Such being the case not only will most of the energy be directed towards the bottom but the second system b, when considering a the first system, will be outside the cone of great intensity so that no sound from a will reach 6. This is advantageous in depth sounding since the greatest amount of energy possible will be directed towards the bottom while at the same time the receiving system may be shielded. If both a and b are directive, one receiving and the other sending, then the receiver b can be made directive for reception from the bottom in which case it will be very insensitive to the effect of the direct sound since sound received from the direction of the sender will arrive along the line of zero sensitivity. This is shown diagrammatically in Figure 9. By placing the receiver on one side of the vessel and the sender upon the other the additional screenin from the vessel may be obtained.

igures 1111, b and 0 show the application to binaural listening. Here the spacing should be equal to pensation is introduced but the base merely rotated, the spacing need only be in order to avoid an ambiguity by a double image. Figures 11a, 6 and 0 show the additional feature of using the central receivers for both the right and left base.

In Figure 11 two receivers 3 and 4 are shown close together, 3 serving for the left base T, and 4 serving for the right base T This is equivalent to having one receiver serve in common for the right and left. Similarly there is no objection to having the bases overlap or to have a common center region serve for both the right and left-base as shown in Figures 11?; and 110. In each of these cases the left base is connected to telephone T and the right to T In order to produce a binaural image it is necessary of course to have the end receivers connected only to one ear, as shown in 11 where 1 is connected only to T and 6 to T Where compensation is to be introduced, as shown in Figure 12 where receivers 1, 2, 8 and 4 are connected to the left side of the compensator 20 and receivers 3, 4, 5 and 6 are connected to the right side of the compensator, it is necessary to space the receivers one half the distance apart they would otherwise be spaced. The spacing in this case is n- 1 Zn in order to avoid ambiguity of double images. This results from the fact that by compensation the apparent spacing between receivers can be doubled, since the amount of compensation to bring about a balance for any direction (the direction along the axis requiring the most compensation) requires a compensation equivalent to the spacing between the receivers or that the artificial spacing plus the natural spacing, equaling twice the natural spacing, requires the receivers to be. placed just half the ordinary distance in order to avoid a double maximum.

Having now described our our invention we claim 1. A. method of preventing objectionable vibrations in undesired regions in operation of sound transmitters which comprises spacing n said transmitters in a straight line perpendicular to'the plane in which it is desired to prevent said vibration operating said transmitters at a definite frequency such that the spacing of said a transmitters satisfies the relation times the wave length.

2. A method of reducing the base length in binaural reception which consists in spac- 1 of a known wave length substantially in a plane and for receiving similarly propagated wave energy, substantially free from dis turbance of energy propagated in other.

manner, comprising three or more operating units, n in number, spaced in a straight line perpendicular to the plane in which the wave is being propagated, and at a distance equal to times the Wave length of the transmitted or received energy.

4. In a system for receiving wave energy propagated in a plane substantially free from disturbance of energy propagated in other manners, three or more receiving units, n, in number, compensating means for retarding'the Wave energy received by the various receiving units, said receiving units being spaced in a straight line perpendicular to the plane in which the Wave is being propagated, and at a distance such that the actual distance plus the equivalent distance of compensation is equal to 'n times the wave length.

5. In a system for the directive reception of sound waves comprising a. plurality of receiving units spaced in a straight line the spacing between units being n-l 2n tively, said retardation in efiect changing the orientation of said straight line.

6. In a system for the'directive sending of sound waves comprising a plurality of sending units spaced in a straight line, the spacing between units being tures.

WALTER HAHNEMANN.

HEINRICH HEGHT, BERNHARD NIELSEN. 

